On the archetype and homologies of the vertebrate skeleton / by Richard Owen.

  • Richard Owen
Date:
1848
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Licence: Public Domain Mark

Credit: On the archetype and homologies of the vertebrate skeleton / by Richard Owen. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

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    fil exist in the ordinary or endo-skeleton of other vertebrata. The lea Professor of Comparative Anatomy in King’s College, London, who reg this as “the more philosophical mode of considering them*,” has brj stated the homologies proposed by the supporters of this view, viz. thatj opercular bones are gigantic representatives of the ossicles of the ear (H Geoffroy, Dr. Grantf): or that they are dismemberments of the lower (De Blainville, Bojanus),—a view refuted by the discovery of the con j cated structure of the lower jaw in certain fishes, which likewise possess^ opercular bones: he then cites a third view, viz. that they are parts ofi[ dermal skeleton; “in short, scales modified in subserviency to the breatlj function;” an opinion which Professor Jones frankly states tjiat he den from my Lectures on Comparative Anatomy, delivered at St. Bartholom Hospital in 1835, and which he adopts, although its accordance with his proposition is not very clear. I have subsequently seen reason to modify view, though it has received the sanction of the greatest ichthyologist of [ present day, M. Agassiz; and, as I have since found, had presented itsel{ early as 1826, under a peculiar aspect to the pliilosophical mind of Profe;] Von Baer. In his admirable paper on the endo- and exo-skeleton, M. Von Bl expresses his opinion, that the opercular bones are (dermal) ribs or latl portions of the external cincture of the head ji. The idea of the relations! of the opercular flaps to locomotive organs is presented by Carus, under fanciful view of their homology with the wing-covers of beetles and the vail of a bivalve shell §. In 1836, M. Agassiz propounded his idea of the relatl of the opercular bones to scales in a very precise and definite mannl though, as 1 have elsewhere shown ||, the chief ground of his opinion is eij neous. He says, “Les pieces operculaires des poissons ne croissent comme les os des vertebres en general, par irradiation d'un ou de plusie:| points d’ossification; ce sont, au contraire, des v^ritables ecailles, fornuj comme cedes qui recouvrent le tronc, de lames deposees successivemi les unes sous les autres, et dont les bords sont sou vent meme dentcl comme ceux des Readies du corps. Tels sont I’opercule, le sub-opercule, * Professor Rymer Jones, General Outline of the Animal Kingdom, 8vo, 1841, p. 509.1 t Lectures, Lancet, Jan. 11, 1834, p. 573; Outlines of Comp. Auat. p. 64. In mancher Beziehung gehiiren die Kiemcndeckel zu ihr, und ich halte sie um:l mehr fiir (Haut) Uippen, d. h. fiir Seitentheile der iiussern Ringe des Kopfes, da ich sie aa in den gewohulichen Knockenfischen fiir nichts anderes ansehen kann. Hat bei diesen a', der oberste Knocheu des Kiemendeckels wenig Aehnlichkeit mit Rippen, so geht dageyj der unterste so unverkennbar in die strahlender Kiemenhaut iiber, das der Uebergang nicht zu verkennen ist.”—Meckel’s Archiv, 1826, 3 heft, p. 369. An analogous idea of the relation of the opercnlar bones to the inferior or costal arches s proposed by GeoftVoy St. Hilaire (see Annales des Sciences, t. iii. pi. 9, and Cuvier, Hist. Poissons, i. p. 232), and has been adopted by the learned Professor of Comparative Ah toniy in University College, who, speaking of the occipital vertebra:, says, “ The two exter.: and the two latcrd occipitals form the upper arch, and the two opercular and two si- opercular bones constitute the lower arch.” (Lectures, Lancet, 1834, p. 543.) He sub quently, however, adopts and illustrates (p. 573) the homology of the opercular bones w- the ‘ossicula auditus’ of mammalia; and in the ‘Outlines of Corap. Anat.’ cites only t Spixian and Blainvillian hypotheses (pp. 64, 65). In ray Hunterian Lectures (vol. ii. ISi- pp. 113, 130), I have adduced the grounds which have led me to the conclusion that t opercular boues are neither ribs of the exo-skeleton, nor inferior arches of the endo-skeletc but persistent radiating appendages of au inferior (ha:mal) arch; not, however, of the occipi vertebra, but of the frontal; just as the branchiostegal rays are the appendages of the hnent arch of the parietal, and the pectoral fins of that of the occipital vertebra:. That jiarts • both endo- and exo-skeleton may combine to constitute the opercular fin is the more pr bable, inasmuch as we see the same combination of cartilaginous and dermal rays in t pectoral fins of the plagiostomes, and in the median fins of most fishes. § Urtheilen des Knocheu und Schaleugeriistes, fol. p. 122.